Look at any enduring Logo on any famous automobile.
Look at any simple school prefects badge.
Any shield, theatre frontage, look at the the movies credits.
Look at at any precious stone in its setting, or a watch face.

Eventually realise the artistic benefits to be had by borrowing from the heraldic principle of always putting a colour on a metal, or a metal on a colour, however thin be the transition. This is deeply ingrained in our perceptions, has endured for a thousand years. It is not something easily passed by in a blur of post-modern abitrary choice, and is partly driven by the way the eye-brain interface interprets colour and luminance value transitions.

I think the logos could be improved, without even changing them in any fundamental way, by giving them the metal trims they deserve. It would be like putting back the trim on a 2-tone car after a paint job. It speaks of quality and attention to detail, such as would be applied by craftsmen, whatever their field.

The Chevrolet logo breaks the heraldic rules, but because of the border greyscale contrasts, achieves definition reinforced by the choice of lettering.

The Alfa Romeo logo obeys the heraldic rules, and is hence striking, with the monochrome components of the "metals" providing the definition of the outlines. A colour change is given a monochromatic transitional edge by deliberately introducing the metal.
About here is a good place to compare the Sabayon logo set alongside several others.
It is in fact much better to compare them at http://distrowatch.com/, but they change there so often that I shall try and make the point with what we have.
Notice how the Zenwalk logo requires white (from silver) thin line to show the dolphin. At least they exploit the contrast available from opposite ends of the spectrum for the lettering, BUT THEY RETAIN THE WHITE TRANSITION ! It may not be a great logo for other reasons, but the rule holds.
In all the Linux logos, though one may argue their other artistic merits, they manage show their outlines.
The colours for the Sabayon theme are relentlessly taken from a limited section of the spectrum, and so by colour alone, can never achieve the impact of, for example, the Google logo, which is placed on white, and may be endlessly messed about without losing its identity. http://www.logoogle.com/fun-google-logos01.htm

Liking the colours, or not, is definitly not the point. Instead it is to appreciate that the human eye sensors perceive high-bandwidth luminance detail in black-and-white only, and that the resolution available for colour borders is much lower . This is a fact exploited by TV signal modulation mechanisms to save bandwidth. Even in colour printing, the yellow, cyan and magenta inks need the final black ink greyscale overprinted to deliver the luminance detail.

One could print the Sabayon logo without any luma information, and the definition of its component shapes suffers because of it! I recognise that this is a combined artistic and scientific critique, and that it is more than 2 cents worth. I hope you forgive me - they did ask how we felt about it!